You are completely correct that civil law jurisdictions have already solved this: Germany, Estonia, and many others have the all the requirements: a register of all persons available to the central authority, and crypto infrastructure to make it work.
What's missing from the UK, Canada, USA, etc. is the first part! It is hard to believe if you live in Germany, but there really is no big master list of people in those countries. There are many (many, many) lists, linked badly by many different ids. The tax registry, pension registry, drivers license registry, and visa registry are some of the big ones.
Things could be so much simpler if we had such a thing, but the politics between here and there are basically impossible.